Sample handling strategies for the determination of persistent trace organic contaminants from biota samples

Even after emergence of most advanced instrumental techniques for the final separation, detection, identification and determination of analytes, sample handling continues to play a basic role in environmental analysis of complex matrices. In fact, sample preparation steps are often the bottleneck for combined time and efficiency in many overall analytical procedures. Thus, it is not surprising that, in the last two decades, a lot of effort has been devoted to the development of faster, safer, and more environment friendly techniques for sample extraction and extract clean up, prior to actual instrumental analysis. This article focuses on the state of the art in sample preparation of environmental solid biological samples dedicated to persistent organic pollutants (POPs) analysis. Extraction techniques such as Soxhlet extraction, sonication-assisted extraction, supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), pressurised liquid extraction (PLE) and matrix solid-phase dispersion (MSPD) are reviewed and their most recent applications to the determination of POPs in biota samples are provided. Additionally, classical as well as promising novel extraction/clean-up techniques such as solid phase microextraction (SPME) are also summarized. Finally, emerging trends in sample preparation able to integrate analytes extraction and their adequate clean-up are presented.     

Organic Compounds in Surface and Deep Antarctic Snow

Abstract

Eight surface snow samples taken during the 1987/88, 1988/89 and 1990/91 Italian Antarctic Expeditions and six samples collected at different depths from two dissimilar sites during the 1990/91 Expedition, were analyzed for the non-chlorinated organic content using the GC capillary columns technique and GC-MS. Several biogenic and anthropogenic classes of organic compounds were identified and quantitatively determined. The data obtained give a more complete picture of the pollution level in Antarctica.     

Novel method for determining DDT in vapour and particulate phases within contaminated indoor air in a malaria area of South Africa

The organochlorine insecticide DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) is still used for malaria vector control in certain areas of South Africa. The strict Stockholm Convention on Persistent Organic Pollutants (POPs) allows spraying on the inside of traditional dwellings with DDT. In rural villages contaminated dust presents an additional pathway for exposure to DDT. We present a new method for the determination of DDT in indoor air where separate vapour and particulate samples are collected in a single step with a denuder configuration of a multi-channel open tubular silicone rubber (polydimethylsiloxane (PDMS)) trap combined with a micro quartz fibre filter. The multi-channel PDMS trap section of the denuder concentrates vapour phase insecticide whereas particle associated insecticide is transferred downstream where it is collected on a micro-fibre filter followed by a second multi-channel PDMS trap to capture the blow-off from the filter. The multi-channel PDMS trap and filter combination are designed to fit a commercial thermal desorber for direct introduction of samples into a GC–MS. The technique is solvent-free. Analyte extraction and sample clean-up is not required. Two fractions, vapour phase and particulate phase p,p′-DDT, o,p′-DDT; p,p′-DDD, o,p′-DDD; p,p′-DDE and o,p′-DDE in 4 L contaminated indoor air, were each quantitatively analysed by GC–MS using isotopically labelled ring substituted ¹³C₁₂ – p,p′-DDT as an internal standard. Limits of detection were 0.07–0.35 ng m⁻³ for p,p′-DDT, o,p′-DDT, p,p′-DDD, o,p′-DDD, p,p′-DDE and o,p′-DDE. Ratios of airborne p,p′-DDD/p,p′-DDT and of o,p′-DDT/p,p′-DDT are unusual and do not match the ideal certified ingredient composition required of commercial DDT. Results suggest that the DDT products used for indoor residual spraying (IRS) prior to, and during 2007, may have been compromised with regards to insecticidal efficacy, demonstrating the power of this new environmental forensics tool.     

Persistent organic pollutants in edible fish: a human and environmental health problem

Many persistent organic pollutants (POPs) pose serious health hazards to both the environment and human. Among these, polychlorobiphenyls (PCBs) are probable human carcinogens and can also pose non-cancer health hazards to intellectual functions and the nervous, immune and reproductive systems. The risks and hazards associated with POP residues in tissues are a function of the dioxin-like compound toxicity and an individual's exposure. Fish consumption might become a serious problem because of bioaccumulation as revealed in many studies worldwide.We report data concerning the accumulation and pattern of hexachlorobenzene (HCB), p,p′-DDE and PCBs in edible tissues of commercial fish species (bluefin tuna Thunnus thynnus, swordfish Xiphias gladius, Atlantic mackerel Scomber scombrus) from Italian Seas and of the Antarctic toothfish Dissostichus mawsoni from the Ross Sea (Antarctica). The species analyzed are part of the human diet. 2,3,7,8-TCDD toxic equivalents (TEQs) and tolerable weekly intake (TWI) were also calculated to evaluate the toxic hazard for the population that include them in their diet.Gaschromatography revealed 0.16±0.24 and 0.4±0.2 ng/g wet wt of HCB in Antarctic toothfish and bluefin tuna, respectively. p,p′-DDE concentrations were 38±29 and 31±38 ng/g wet wt in swordfish and bluefin tuna muscle, respectively, and 0.66±0.57 ng/g wet wt in the Antarctic toothfish. PCBs showed higher concentrations and they were 89±82, 80±86 and 5.2±4.0 ng/g wet wt in the muscle of swordfish, bluefin tuna and Antarctic toothfish, respectively. In Mediterranean fish, the most abundant congeners were the most persistent PCB numbers 153, 138, 180, 118 and 170, which accounted for 51% and 47% of the total PCB residue in tuna fish and swordfish, respectively, and 18% in the Antarctic toothfish. TEQs were 1.97 and 4.65 pg/g wet wt in bluefin tuna muscle and gonads, respectively, and 0.11 pg/g wet wt in Antarctic toothfish. The TEQ weekly intake was calculated and values ranged 197–465 pg_TEQ/week when consuming 100 g of Mediterranean fish and therefore lower than the recommended TWI. Those values were higher (788–1860 pg_TEQ/week) than the recommended TWI, if 400 g of fish/week was consumed (with the exception of Antarctic fish).     

Analysis of persistent organic pollutants in marine sediments using a novel microwave assisted solvent extraction and liquid-phase microextraction technique

A simple and novel analytical method for quantifying persistent organic pollutants (POPs) in marine sediments has been developed using microwave assisted solvent extraction (MASE) and liquid-phase microextraction (LPME) using hollow fibre membrane (HFM). POPs studied included twelve organochlorine pesticides (OCP) and eight polychlorinated biphenyl (PCB) congeners. MASE was used for the extraction of POPs from 1 g of sediment using 10 ml of ultrapure water at 600 W for 20 min at 80 degrees C. The extract was subsequently subjected to a single step LPME-HFM cleanup and enrichment procedure. Recovery varied between 73 and 111% for OCPs; and 86-110% for PCBs, and exceeded levels achieved for conventional multi-step Soxhlet extraction coupled with solid-phase extraction. The method detection limit for each POP analyte ranged from 0.07 to 0.70 ng g(-1), and peak areas were proportional to analyte concentrations in the range of 5-500 ng g(-1). Relative standard deviations of less than 20% was obtained, based on triplicate sample analysis. The optimized technique was successfully applied to POP analysis of marine sediments collected from the northeastern and southwestern areas of Singapore's coastal environment.     

全二维气相色谱-电子捕获检测器法分析土壤中毒杀芬同类物的残留

建立了全二维气相色谱-电子捕获检测器(GC× GC-μECD)检测土壤中毒杀芬同类物的分析方法.以非极性的DB- XLB(20 m×0.25 mm×0.25 μm)为第一色谱柱,中等极性的BPX-50(2 m×0.1 mm×0.1 μm)为第二色谱柱,对土壤中23种高关注毒杀芬同类物进行了分离鉴定,并采用基质曲线外标法进行定量分析.本方法在1～200,μg/L浓度范围内,毒杀芬同类物的线性相关系数(r2)均大于0.99,方法检出限(S/N=3)为0.039～0.482 μg/L,基质加标毒杀芬同类物的回收率为55％～115％,相对标准偏差(RSD)均小于30％(n=5).利用本方法对毒杀芬污染的土壤样品进行了测定,获得了较好的分离效果.     

Evaluation of the capabilities of atmospheric pressure chemical ionization source coupled to tandem mass spectrometry for the determination of dioxin-like polychlorobiphenyls in complex-matrix food samples

The use of the novel atmospheric pressure chemical ionization (APCI) source for gas chromatography (GC) coupled to triple quadrupole using tandem mass spectrometry (MS/MS) and its potential for the simultaneous determination of the 12 dioxin-like polychlorobiphenyls (DL-PCBs) in complex food and feed matrices has been evaluated.     

基质固相分散-气相色谱串联质谱法测定孕妇血清中22种持久性有机污染物

建立了基质固相分散技术-气相色谱串联质谱法(MSPD-GC-QQQ-MS/MS)同时测定孕妇血清中22种持久性有机污染物(艾氏剂、狄氏剂、七氯、灭蚁灵、六六六、多氯联苯和滴滴涕)的方法.血清样品与C18吸附剂混合净化,正己烷溶液洗脱,GC-QQQ-MS/MS测定.采用Agilent J&W DB-35ms (30 m×0.25 mm×0.25 μm)分离,正电子离子源(EI+)模式电离,多反应监测模式(MRM)下进行测定,外标法定量.结果表明,在1.0～1000.0 ng/mL的范围内,22种持久性有机污染物的相关系数均大于0.99;在2.0和20.0 ng/mL的添加水平下,所有持久性有机污染物回收率均在75％～ 115％之间,方法定量限均≤0.15 ng/mL.在比较基质固相分散(MSPD)、液液萃取(LLE)和固相萃取(SPE)提取和净化实际加标血清样品时,MSPD方法的结果中位数更接近真实值,且离散程度最小.本方法适用于人类血清中多种持久性有机物的定性和定量分析.     

Comparison of five extraction methods for measuring PCBs,PBDEs, organochlorine pesticides,and lipid content in serum

An increasing number of studies use blood obtained noninvasively to monitor organohalogen contaminants; however, blood can be difficult to analyze because of its aqueous nature and high protein content. We compared five methods for extracting polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides, and lipids from serum using National Institute of Standards and Technology Standard Reference Material 1589a PCBs, Pesticides, PBDEs, and Dioxins/Furans in Human Serum. Liquid:liquid (LLE), cavity-dispersed microwave-assisted (MAE), focused microwave-assisted (FME), solid-phase (SPE), and pressurized fluid (PFE) extraction techniques were compared. FME extraction yielded the optimal recovery of internal standards (IS). All methods resulted in similar contaminant concentrations that also agreed with the certified values for SRM 1589a, except for only a few compounds measured by methods other than FME. Based on these findings, the FME method was determined to be the best overall extraction method. One procedural factor was found to affect contaminant concentrations; use of IS carrier solvents that were immiscible with serum (or when the serum was not directly physically mixed with IS) resulted in a 30% underestimation of organohalogen concentrations. This study offers valid, novel extraction alternatives beyond traditional methods (e.g., LLE) for blood contaminant measurements. Figure       

Improved quality control in gas chromatography interfaced to stable isotope ratio mass spectrometry by application of derivative chromatography

Compound-specific isotope analysis using gas chromatography interfaced to isotope ratio mass spectrometry (GC-IRMS) is a versatile technique for applications ranging from source appointment and the elucidation of biochemical pathways. When δ¹³C values are going to be determined, the sample is combusted to CO₂ and the resulting gas is analyzed relative to a standard with known stable carbon isotope ratio. With the combustion step any information on the identity of a peak is lost. Co-eluting compounds can no more be identified which can lead to significant alterations of the δ¹³C value of the analyte. For improvement of the QA/QC protocols in GC-IRMS, we used first, second, and third order derivative chromatography. The suitability of the technique was studied using mixtures of 2,3,3′,4,4′,5,5′-heptachloro-1′-methyl-1,2′-bipyrrole (Q1) and 2,2′,4,5,5′-pentachlorobiphenyl (PCB 101). By application of different GC oven programs four scenarios ranging from baseline separation to full co-elution were obtained. Derivative chromatography enabled identification of the interference of Q1 with PCB 101 even when both peaks fully co-eluted. Although the δ¹³C values could not be determined from interfered scenarios, the use of derivative spectroscopy will help to prevent acceptance of incorrect data due to co-elutions. Derivative chromatography was finally used to study the peak purity of 2,2′,3,4,4′-pentabromodiphenyl ether (BDE 85) in technical pentabromo diphenyl ether (DE-71). Already the first order derivative demonstrated that this key-BDE congener was interfered by a compound identified as 2,2′,4,4′,6,6′-hexabromodiphenyl ether (BDE 155).     

A simple and fast liquid–liquid extraction method for the determination of 2,2′,4,4′,5,5′-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p′-DDE) from human serum for epidemiological studies on type 2 diabetes

A simple and fast method is presented to be used for example in studies on the relationship between serum levels of persistent organic pollutants and type 2 diabetes mellitus. Method is based on liquid–liquid extraction and gas chromatography coupled with high-resolution mass spectrometry. In the sample pre-treatment special attention was paid to minimize the number of sample manipulation steps and the amounts of organic solvents needed. Compounds analyzed were 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p′-DDE), the major metabolite of DDT. The method included extraction and cleanup of 0.2 ml of serum in a single test tube and subsequent analysis of the extract from 0.2 ml final volume. Validation was conducted to explore the performance of the method. The limits of detection for p,p′-DDE and PCB-153 based on the standard deviation of the blank samples were 4.3 and 3.1 pg/ml, respectively. Repeatability was less than 2.5% at three concentration levels tested and recovery from Certified Reference Material SRM 1589a was 84% for p,p′-DDE and 87% for PCB-153 of the certified values, respectively. Serum samples from the AMAP intercalibration round 2008-2 were also analyzed, and results were 101–116% of the assigned values. The presented method was used for an epidemiological study with more than 700 serum samples from a type 2 diabetes cohort from Sweden.     

Two multidimensional chromatographic methods for enantiomeric analysis of o,p′-DDT and o,p′-DDD in contaminated soil and air in a malaria area of South Africa

In rural parts of South Africa the organochlorine insecticide DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) is still used for malaria vector control where traditional dwellings are sprayed on the inside with small quantities of technical DDT. Since o,p′-DDT may show enantioselective oestrogenicity and biodegradability, it is important to analyse enantiomers of o,p′-DDT and its chiral degradation product, o,p′-DDD, for both health and environmental-forensic considerations. Generally, chiral analysis is performed using heart-cut multidimensional gas chromatography (MDGC) and, more recently, comprehensive two-dimensional gas chromatography (GC × GC). We developed an off-line gas chromatographic fraction collection (heart-cut) procedure for the selective capturing of the appropriate isomers from a first apolar column, followed by reinjection and separation on a second chiral column. Only the o,p′-isomers of DDT and DDD fractions from the first dimension complex chromatogram (achiral apolar GC column separation) were selectively collected onto a polydimethylsiloxane (PDMS) multichannel open tubular silicone rubber trap by simply placing the latter device on the flame tip of an inactivated flame ionisation detector (FID). The multichannel trap containing the o,p′-heart-cuts was then thermally desorbed into a GC with time-of-flight mass spectrometry detection (GC–TOFMS) for second dimension enantioselective separation on a chiral column (β-cyclodextrin-based). By selectively capturing only the o,p′-isomers from the complex sample chromatogram, ¹D separation of ultra-trace level enantiomers could be achieved on the second chiral column without matrix interference. Here, we present solventless concentration techniques for extraction of DDT from contaminated soil and air, and report enantiomeric fraction (EF) values of o,p′-DDT and o,p′-DDD obtained by a new multidimensional approach for heart-cut gas chromatographic fraction collection for off-line second dimension enantiomeric separation by ¹D GC–TOFMS of selected isomers. This multidimensional method is compared to the complementary technique of comprehensive GC × GC–TOFMS using the same enantioselective column, this time as the first dimension of separation.     

Streamlined sample cleanup using combined dispersive solid-phase extraction and in-vial filtration for analysis of pesticides and environmental pollutants in shrimp

A new method of sample preparation was developed and is reported for the first time. The approach combines in-vial filtration with dispersive solid-phase extraction (d-SPE) in a fast and convenient cleanup of QuEChERS (quick, easy, cheap, effective, rugged, and safe) extracts. The method was applied to simultaneous analysis of 42 diverse pesticides and 17 environmental contaminants, including polycyclic aromatic hydrocarbons, polychlorinated biphenyls (PCBs), and flame retardants, in shrimp as the sample matrix. Final extracts were analyzed by both low-pressure gas chromatography – triple quadrupole tandem mass spectrometry (LPGC-MS/MS), and high-performance liquid chromatography – triple quadrupole tandem mass spectrometry (HPLC-MS/MS) to provide a wide scope of analysis for targeted analytes. During method development, several different commercial sorbents for d-SPE were investigated and compared with respect to analyte recoveries. The method was validated at 10, 50, and 100 ng g⁻¹ spiking levels (10-fold lower for PCBs), and the results for nearly all analytes were between 70 and 115% recoveries with ≤17% relative standard deviations. The method was shown to be simple, fast, and effective for multi-application analysis of chemical residues in the representative food and environmental marker matrix.     

A new cleanup method of dioxins in sediment using large volume injection gas chromatography online coupled with liquid chromatography

A new cleanup method was developed and validated for the determination of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in sediment. The sample extract was first treated with sulfuric acid and then cleaned up by a large volume injection gas chromatography online coupled with liquid chromatography (LVI-GC-LC) system. PCDD/Fs in the extract were separated by a GC column (DB-5), selected cut, cool trapped and transferred to a LC column (alumina). The fraction of PCDD/Fs eluted from the alumina column was collected and concentrated for the instrumental analysis. Under the optimized conditions, LVI-GC-LC method achieved the recoveries of 57–102% for 2,3,7,8-substituted PCDD/Fs, which met the requirements of US Environmental Protection Agency (EPA) Method 1613 and were better than those obtained using the conventional multistep column cleanup method. Meanwhile, compared with the conventional method, the limit of detection (LOD) values of 2,3,7,8-substituted PCDD/Fs cleaned up by LVI-GC-LC method were decreased due to the high-efficiency removal of interferents. These results suggested that the LVI-GC-LC cleanup method was a promising alternative to the multistep cleanup procedure for the determination of dioxins in environmental samples.     

Analytical chemistry of the persistent organic pollutants identified in the Stockholm Convention: A review

Persistent organic pollutants (POPs) are major environmental concern due to their persistence, long-range transportability, bio-accumulation and potentially adverse effects on living organisms. Analytical chemistry plays an essential role in the measurement of POPs and provides important information on their distribution and environmental transformations. Much effort has been devoted during the last two decades to the development of faster, safer, more reliable and more sensitive analytical techniques for these pollutants. Since the Stockholm Convention (SC) on POPs was adopted 12 years ago, analytical methods have been extensively developed. This review article introduces recent analytical techniques and applications for the determination of POPs in environmental and biota samples, and summarizes the extraction, separation and instrumental analyses of the halogenated POPs. Also, this review covers important aspects for the analyses of SC POPs (e.g. lipid determination and quality assurance/quality control (QA/QC)), and finally discusses future trends for improving the POPs analyses and for potential new POPs.